In 793 the monks on the island of Lindisfarne, off the northeast coast of England, are unpleasantly surprised by the arrival of violent raiders from the sea. Their misfortune is the first clearly dated event in the saga of the Vikings - the last and most dramatic exodus in the long story of migration from Scandinavia, the original home of the Goths and Vandals.

The name Viking is thought to derive from vikingr, a word for 'pirate' in the early Scandinavian languages. It accurately describes the Norsemen who for two centuries raid the coasts of Britain and of northwest France. But in many places the Scandinavians also settle - in the islands of the north Atlantic, in the British Isles, in Normandy, in Sicily and in the very heart of Russia.

It is impossible to assign the various Viking groups at all precisely to places of origin. But broadly speaking, adventurers from the coast of Norway raid the north of England and continue round the Scottish coast to Ireland. Vikings from the same region later settle in the Scottish islands, Iceland and parts of Ireland.

The Vikings invading eastern Britain and northwest France, and eventually settling in both regions, come mainly from Denmark. The Swedes raid across the Baltic and penetrate deep into Russia as traders.

Turks and Mongols: 6th - 13th century

The high plateau of Mongolia, east of the Altai mountains, is rivalled only by Scandinavia as a region from which successive waves of tribesmen have emerged to prey upon more sedentary neighbours. Mongolia is the original homeland of both Turks and Mongols, two groups much intermingled in history and loosely related in their languages.

Mongolia is an ideal starting point for the movement of nomadic tribes in search of new pastures, and for sudden excursions of a more predatory nature. It lies at the extreme end of an unbroken range of open grasslands, the steppes, which reach all the way to Europe. Horsemen can move fast along the steppes. South of this nomadic highway live rich settled communities.

The emergence of the Turks from Mongolia is a gradual and uncharted process. Each successive wave makes its first appearance in history only when Turkish tribes or warriors acquire power in some new region, whether they be the Khazars, the Seljuks or one of many other such groups.

The sudden eruption of the Mongols from their homeland is different. Their astonishing expansion, spanning the breadth of Asia, can be precisely dated (to the early years of the 13th century) and can be attributed to the military genius of one man - born with the name of Temujin, but known now as Genghis Khan.

Magyars: 9th - 10th century

The lower Danube, before the river enters the Black Sea, has been Europe's doorway to tribal groups arriving from the north and east. Here the Visigoths and Ostrogoths and Slavs have first presented themselves to the Roman empire, requesting or demanding admission. And here there arrives, in889, another group.

They differ from their predecessors in that they are not Indo-Europeans. They speak a Finno-Ugric language. They call themselves Magyars, but their federation of tribes is known as On-Ogur, meaning 'Ten Arrows'. The pronunciation of On-Ogur by their new Slav neighbours leads, eventually, to the name by which the Magyars are later known - Hungarians.

The Magyars have been living for several centuries near the mouth of the Don, as vassals of the Khazars. From 889 they spend a few years in the Balkans in the service of the Byzantine emperor, but soon they move on to the northwest, through the Carpathian mountains.

Since 890 their leader has been Arpad, elected prince by the chieftains of the seven Magyar tribes. His people number no more than 25,000, but together they subdue (within the space of a few years) the scattered population of the region now known as Hungary. So Arpad becomes the founder of a nation which somehow - in all the upheavals of central Europe - retains its identity and its language down through the centuries.

The rise of the Seljuks: 10th - 11th century

Seljuk is the chieftain of a group of Turkish tribes who migrate, in the late 10th century, from the steppes to the northern borders of the Persian empire - in the region around the Syr-Darya river. They embrace Islam, and are expected to play their part in the frontier defences of the Muslim world. But in the recurrent pattern of barbarians in the suburbs of civilization, they have their own ideas. They fancy a more central position.

The obvious stepping stone towards greater power is the newly formed Turkish realm, founded by Mahmud and centred on Ghazni. Mahmud, an experienced conqueror, dies in 1030. His son, Mas'ud, becomes the focus of Seljuk attention.

Mas'ud is campaigning in the eastern part of his empire, in India, when Togrul Beg, a grandson of Seljuk, strikes in the west. Mas'ud hurries home to confront this threat. He meets the Seljuk army in 1040 at Dandandqan, to the northeast of Mashhad, and is defeated.

The Seljuks establish their base in this border region between modern Iran and Afghanistan, while Togrul Beg looks further west for even greater prizes. Persia is in a state of anarchy, ruled by many petty princes (the majority of them Shi'as). The authority of the Sunni caliph in Baghdad is no more than nominal.

Togrul Beg gradually fights his way westwards through Persia. By 1055 he is in a position to enter Baghdad itself. He does so without violence, being welcomed by the caliph as a liberator from the Shi'as. The caliph gives him the title of sultan and an ambitious task - to overwhelm the Fatimids, the Shi'ite dynasty controlling the caliph's Egyptian territories.

This is beyond the powers of Togrul Beg and his still somewhat unruly Turkish tribesmen. But for the next two generations the Seljuk dynasty retains control in Baghdad and governs a Persian empire restored to extensive boundaries.

Byzantines and Turks: 1064-1071

In 1064 the Seljuk Turks, under their sultan Alp Arslan, invade Armenia - for many centuries a disputed frontier region between the Byzantine empire and neighbours to the east. Alp Arslan follows his success here with an attack on Georgia, in 1068. These acts of aggression prompt a response from the Byzantine emperor, Romanus IV Diogenes.

The armies meet in 1071 at Manzikert, near Lake Van. The battle, a resounding victory for the Seljuks, is a turning point in the story of the Byzantine empire. Within a few years there are Turkish tribes in many parts of Anatolia. Some of them are bitter enemies of the Seljuks, but the Seljuks are now the main power in this borderland between Islam and Christianity.

Throughout the 12th and 13th century Anatolia is in turmoil. Turkish tribes fight among themselves. The Byzantines try to recover their land. Crusaders, passing through and from 1204 occupying Constantinople, complicate the picture.

But the new and overriding feature is that Anatolia is now largely occupied by Turks. This fact enters the languages of the period. In addition to its many other names, the region begins to be referred to as Turkey - the land of the Turks. The new identity survives the arrival of the Mongols in the 13th century and the end of the Seljuk dynasty in the early 14th century. By then another Turkish tribe, the Ottomans, are making their mark.

Crusaders moving east: 11th - 12th century

In April 1095 an unusually large shower of meteors, moving rapidly through the sky, prompts a significant interpretation by the bishop of Lisieux. It means, he says, that there will soon be a great movement of Christians towards the holy places.

Maybe the bishop is already playing his part in promoting such a movement. In March of this same year the Byzantine emperor has appealed for Christian help against the Turks. In November the pope preaches a crusade to recover the holy places of Christendom.

During 1096 western Christians duly make their way in large numbers towards Constantinople. In the early autumn a plague of locusts in the Byzantine empire is seen as providing an apt portent of the arrival of the hungry hordes of crusaders. The locusts destroy the vines but leave the corn - resulting in an interpretation even stranger than the bishop's response to meteor showers.

The meaning, they say, is that the crusaders will not harm Byzantine Christians (associated with corn and the bread of life) but will damage the Muslims (linked with the vine, rather unconvincingly in view of the Qur'an's prohibition of alcohol).

As a result of this first crusade, for most of the 12th century there are Christian kingdoms along the eastern shores of the Mediterranean, defended and maintained by soldiers and traders from western Europe.

The numbers are small, compared to other movements of people in history, and their stay in the region as rulers is brief. But just as the great castles of Syria are a reminder of the military presence of the crusaders, so the occasional fair-haired and blue-eyed child in villages near the castles still seems - even today - to bear witness to their domestic lives.

The Mongol explosion: 13th century

The aggressive energy of one man, Genghis Khan, lies behind the amazing eruption of the Mongols in the 13th century. In 1215 he reaches and captures Beijing. Samarkand and Bukhara are taken and sacked in 1220. The marauder then heads south and enters India, but he turns back from this rich prize when he reaches the Indus. By 1223 his armies have moved round the Caspian and up through the Caucasus mountains to plunder cities of the Crimea and southern Russia.

This journey of conquest, unmatched in its speed and extent since the exploits of Alexander the Great, is based on brilliant psychological warfare.

Several different factors explain the devastating success of Genghis Khan and his armies, but superior weaponry is not one of them. The traditional riding skill of the nomads of the steppes plays, as ever, a large part; and with stirrups now a standard part of cavalry equipment, the agility of the horsemen is greater than ever, in galloping close to the the enemy, releasing a hail of arrows and wheeling away again.

Horsemanship also plays its part in the system of communication which enables Mongol armies to coordinate their strategies. Riders gallop between well-equipped staging posts across the steppes, enabling a message to travel more than 200 miles in a day. Pigeons, too, are trained for the purpose.

But the single most important element is a ruthless use of two psychological weapons, loyalty and fear. Genghis Khan makes a cunning distinction in his treatment of nomadic tribesmen and the settled inhabitants of cities and towns. A warrior from a rival tribe, who battles bravely against Genghis Khan but loses, will be rewarded for his valour and encouraged to join the Mongols against the rest of the world. Only cowardice or treachery in an opposing tribe are punished.

For sedentary folk in alien lands these rules are reversed. Here treachery is positively encouraged. Spies infiltrate the towns. Informers are sought out and bribed. The Mongols are coming. There is a choice to be made.

The choice is a simple one; to fight or to surrender. News of the consequences travels fast. If a town bravely resists, the inhabitants are massacred in a public display. They are herded outside the walls to confront Mongol troopers with battle-axes. Each trooper is given a quota to despatch. A tally of ears is sometimes demanded as proof that the work is done.

Terror stalks ahead of a Mongol horde like an invisible ally. The spies in the town let it be known that a rapid surrender may well be rewarded with mercy. Usually the citizens need no persuading. The gates are opened. After sufficient plunder to keep the troops happy, the horde moves on.

The sons and grandsons of Genghis Khan continue the expansion of Mongol power after his death in 1227. Their territory reaches its greatest extent when his grandson, Kublai Khan, is both the great khan of the Mongols and the emperor of China. At that time the family's rule stretches from southern China to Korea in the east, and across the whole of Asia to the Euphrates and southern Russia in the west.

This empire, so rapidly built in the 13th century, will collapse almost as suddenly in the 14th. But few people have ever moved so far or so fast, or with such devastating effect, as the Mongol tribesmen.

The Ottoman Turks: 13th - 14th century

During the 13th century, when many Turkish emirates are being established in Anatolia, a petty chieftain by the name of Ertughrul wins control over a limited area around Sögüt, between Ankara and Constantinople. He is succeeded in about 1285 by his son Osman, whose name is a Turkish version of the Arabic Othman. Through Osman, seen later as founder of the dynasty, his people become known as the Ottoman Turks.

Most of the Turks of Anatolia live in a style in keeping with their origins, as fierce nomads of the steppes. Riding out to war is their everyday activity. But they are also keen Muslims. They see themselves as ghazi, an Arabic word for warrior but with religious connotations.

Turks setting out on a ghaza (armed raid) are indulging in an expedition of plunder but also in a jihad (holy war). It is a potent combination. The enfeebled Byzantine empire to the west of their territory - crippled, ironically, by the Christian fourth crusade - provides the Ottoman Turks with a natural target.

Progress is at first slow. The Ottoman horsemen lack the equipment to take fortified Byzantine towns. Instead they plunder the surrounding countryside, effectively strangling their victims into submission. Bursa, the first important Byzantine stronghold to the west, falls to them in 1326, the year of Osman's death.

After the fall of Bursa the Ottoman advance quickens. Nicaea yields in 1331 and Nicomedia in 1337. In that direction a narrow neck of land leads directly to Constantinople, but the Ottomans prefer a roundabout route. In 1354 they cross into Europe at the other end of the sea of Marmara, capturing Gallipoli. Eight years later Adrianople falls to them, severing the main route westwards from Constantinople.

A stranglehold is being applied to the Byzantine capital itself, but the Turks look first for plunder in an easier direction. They continue westwards into the Balkans, where their successes prompt the formation of the formidable Ottoman fighting force known as the Janissaries.

The Turks in the Balkans: 1389 - 1402

A victory at Kosovo in 1389 brings Serbia under Ottoman control as a vassal state. The Ottoman sultan Murad I dies on the battlefield of Kosovo and is succeeded by his son Bayazid I, whose name Yildirim ('Thunderbolt') reflects his early military successes. The Slav kingdom of Bulgaria is fully occupied by 1393. In the following year Bayazid begins the long expected blockade of Constantinople. A Hungarian army marching as a crusade against the Turks is heavily defeated at Nicopolis in 1396. Meanwhile the sultan campaigns south into Greece. But then the Balkans and Constantinople are given a sudden reprieve.

Bayazid is confronted by a major threat in Anatolia - the arrival of Timur.

Retrenchment and recovery: 1402 - 1481

The Ottoman domain shrinks drastically after Bayazid's defeat and capture by Timur in 1402. The many small emirs of Turkey reassert their independence, as do the Balkan states. The three sons of Bayazid are left with only the family's central territories round the southern and western sides of the sea of Marmara. They fight each other in a civil war which is won by the youngest, Mehmed I, in 1413.

From this unpromising position, the son and grandson of Mehmed (Murad II and Mehmed II, whose combined reigns span nearly seventy years) achieve an astonishing recovery for the Ottoman state - posing an ever greater threat to the Byzantine empire.

Murad patiently reasserts control over much of western Anatolia, and makes equivalent headway in the Balkans. Serbia is brought back into the Ottoman fold (Murad marries a Serbian princess in 1433). Much of Bulgaria also is recovered. A strong counter-attack down the Danube in 1443 by an army of Hungarians and Poles is at first successful, until the Ottoman Turks win a decisive victory at Varna in 1444.

This steady process is continued by Murad's son, Mehmed II.

Mehmed II conquers Athens and almost the whole of the Greek peninsula in 1458-60. He then engages in a prolonged war with Venice, winning many valuable ports along the Adriatic coast. In 1463-4 he captures Bosnia where a large number of nobles convert to Islam, unlike neighbouring Serbia which remains largely Greek Orthodox - a distinction with resonance in more recent history. By the time of Mehmed's death, in 1481, Anatolia has also been recovered. Even regions north of the Black Sea are vassal states.

But the achievement which gives Mehmed his title of Fatih (Conqueror), and his secure place in history, has been his capture in 1453 of Constantinople.

Gypsies: from1417

A group of some 200 nomads reach Lüneburg in north Germany in 1417. They are described as Secani. But their arrival is the first precise record of the people now known worldwide as the Gypsies.

Their name in English, and in several other languages, reflects a mistaken notion that they derive originally from Egypt. It is more probable that they come from India, moving west at some time during the medieval centuries. A romantic theory that they descend from 12,000 Indian musicians, brought to Persia for his entertainment by the emperor Bahram Gor in420, is likely to be fanciful.

Whatever their origins, the Gypsies spread rapidly through western Europe during the 15th and 16th centuries. Their refusal to settle and assimilate with the local population enables them to retain a separate identity. But it also provokes hostility and persecution.

This is seen, from the start, in the removal of Gypsies from western kingdoms - akin to the expulsion of Jews (whose sufferings the Gypsies also share in the 20th century). Gypsies are expelled successively from Germany (1497), Spain (1499), France (1504), England (1531), Denmark (1536), Scotland (1541) and Poland (1557).

Invariably the Gypsies have been able to make their way back into forbidden territories, maintaining an international network of their own which transcends frontiers. Their favoured activities - light metalwork (as tinkers), horse-trading (or in modern societies selling second-hand cars), street-selling, fortune-telling, music-making or seasonal agricultural work - always leave the family free to move on.

From as early as the 16th century, state authorities have attempted to force the Gypsies to settle. It is a struggle which continues to this day, when governments have the added incentive of bringing Gypsy children into a state education system.